U.S. patent application number 14/711683 was filed with the patent office on 2015-11-19 for erosion protection sleeve.
The applicant listed for this patent is James E. McGUIRE, Andrew C. STRANGE. Invention is credited to James E. McGUIRE, Andrew C. STRANGE.
Application Number | 20150330231 14/711683 |
Document ID | / |
Family ID | 53491258 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150330231 |
Kind Code |
A1 |
McGUIRE; James E. ; et
al. |
November 19, 2015 |
EROSION PROTECTION SLEEVE
Abstract
Described are articles, materials, and methods for protecting
moving parts from degradation, such as protecting an airfoil or
hydrofoil from erosion forces caused by air, sand, water, or wind.
Described are foil-shaped erosion-resistant sleeves for protecting
a foil. The sleeves may have a body with an outer surface, an inner
surface, a thickness, a longitudinal dimension with a first end and
a second end, and a dimension transverse to the longitudinal
dimension, and the outer surface may include a shape-memory polymer
or an elastomeric polymer with a materially continuous perimeter
circumscribing the body around the transverse dimension, and an
opening at the first end of the body adapted to receive the foil.
Some erosion-resistant sleeves may be installed on a foil by
inserting the foil into the sleeve through an opening in the
sleeve, contracting the sleeve around the foil, and conforming the
sleeve around the foil.
Inventors: |
McGUIRE; James E.; (Tiburon,
CA) ; STRANGE; Andrew C.; (Worthington, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
McGUIRE; James E.
STRANGE; Andrew C. |
Tiburon
Worthington |
CA
OH |
US
US |
|
|
Family ID: |
53491258 |
Appl. No.: |
14/711683 |
Filed: |
May 13, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61992636 |
May 13, 2014 |
|
|
|
Current U.S.
Class: |
428/36.9 |
Current CPC
Class: |
B64C 11/205 20130101;
F01D 5/28 20130101; B64C 27/473 20130101; Y10T 428/139 20150115;
B64C 27/33 20130101 |
International
Class: |
F01D 5/28 20060101
F01D005/28; B64C 27/33 20060101 B64C027/33; B64C 27/473 20060101
B64C027/473 |
Claims
1. An erosion-resistant sleeve for protecting a foil, the foil
comprising an airfoil or hydrofoil having a first foil shape, the
sleeve comprising: a body adapted to cover at least a portion of
the foil, the body comprising an outer surface and an inner surface
and a sleeve thickness therebetween and having a longitudinal
dimension with a first end and a second end and a dimension
transverse to the longitudinal dimension, the outer surface
comprising a shape memory polymer or an elastomeric polymer with a
materially continuous perimeter circumscribing the body around the
transverse dimension and having a second foil shape, the inner
surface comprising a third foil shape that has the same shape as at
least a portion of the first foil shape; and an opening at the
first end of the body adapted to receive the foil.
2. The sleeve of claim 1 wherein the first foil shape comprises a
wing-like curvilinear foil shape or a double wedge foil shape.
3. The sleeve of claim 1 wherein the body is seamless.
4. The sleeve of claim 1 wherein the body further comprises an
opening at a second end.
5. The sleeve of claim 1 wherein the body comprises a concave
portion.
6. The sleeve of claim 5 wherein the concave portion comprises a
non-shape memory material.
7. The sleeve of claim 1 wherein the first foil shape and the
second foil shape are substantially the same.
8. The sleeve of claim 1 wherein the first foil shape and the
second foil shape are different.
9. The sleeve of claim 1 wherein the first foil shape and third
foil shape are substantially the same.
10. The sleeve of claim 1 wherein the third foil shape is adapted
and configured to provide a lift force when the sleeve covers the
foil and the foil moves relative to an air or water current.
11. The sleeve of claim 1 wherein the foil comprises a leading edge
and a trailing edge and the sleeve is adapted to surround and cover
the foil at a portion of the leading edge, a portion of the
trailing edge, and an area between the edges.
12. The sleeve of claim 1 wherein the thickness varies from a first
portion of the body to a second portion of the body.
13. The sleeve of claim 12 wherein the foil includes a rounded
leading edge at the front of the foil and a trailing edge at the
rear of the foil wherein the thickness is greater at the first
portion corresponding to the rounded leading edge.
14. The sleeve of claim 1 wherein the foil and the inner surface of
the body are substantially the same size.
15. The sleeve of claim 1 wherein the inner surface of the body is
smaller than the foil.
16. The sleeve of claim 1 wherein a transverse segment of the body
is adapted to undergo a first expansion change from about 1% to
about 75% in the transverse dimension.
17. The sleeve of claim 1 wherein a transverse segment of the body
is adapted to undergo a first expansion change to provide between
0.010'' and 0.25'' of clearance between the inner surface of the
body and the foil.
18. The sleeve of claim 1 wherein a transverse segment of the body
is adapted to undergo a first contraction change from about 1% to
about 75% in the transverse dimension.
19. The sleeve of claim 1 wherein a transverse segment of the
sleeve is adapted to undergo a first contraction change to remove
between 0.010'' and 0.25'' of clearance between the inner surface
of the body and the foil when the sleeve is in place over the
foil.
20. The sleeve of claim 1 wherein a transverse segment of the body
is adapted to undergo a first expansion change in response to an
expansion force to provide clearance between the inner surface of
the sleeve and an outer surface of the foil, and to contract when
the force is removed and thereby deliver a compressive force over
the surface of the foil when the sleeve is in place over the foil.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/992,636, filed May 13, 2014, which application
is incorporated by reference herein.
INCORPORATION BY REFERENCE
[0002] All publications and patent applications mentioned in this
specification are herein incorporated by reference to the same
extent as if each individual publication or patent application was
specifically and individually indicated to be incorporated by
reference.
FIELD
[0003] The present invention pertains to articles, materials, and
methods for protecting objects from degradation, such as protecting
an airfoil or hydrofoil from erosion forces caused by sand, sun,
water, or wind.
BACKGROUND
[0004] Erosion is the process by which the surface of an object is
worn away over time. The forces of erosion, such as those caused by
sand, sun, water, and wind, can destroy the object. Airplane wings,
helicopter rotor blades, boat hydrofoils and other foils experience
especially strong erosion forces due to their movement through air
or water. Erosion of these foils is a vexing and costly problem
since damaged foils do not perform properly, and fixing or
replacing them can be expensive and result in significant down
time. It is difficult to predict the lifetime of a foil or when a
foil should be replaced as different environments have
significantly different effects on the erosion rates.
[0005] Various products have been developed that attempt to protect
a foil surface from erosion forces, but these products suffer
various limitations. Some commonly used current solutions, such as
protective tape and protective boots (both available from 3M) are
put on an airfoil surface to provide a barrier to erosion forces. A
protective tape for an airfoil is generally a relatively thin,
flexible material with a short, finite length (e.g., shaped like
wide Scotch.RTM. tape) that is placed over part of a foil and held
in place by an adhesive between the tape and the foil. Portions of
the tape may sometimes be overlapped in order to adequately cover
the surface. A boot has typically been preformed from a sheet of
material into a specially shaped applique to fit specifically over
part of the foil surface. Similar to the tape, it is generally held
onto the airfoil surface with an adhesive. A protective tape or
protective boot is typically applied to the leading edge of the
airfoil, which experiences the most severe abrasive and wind
forces, and extends partway along of the top side and bottom side
of the airfoil. Commonly used adhesives for holding boots and tapes
in place include pressure sensitive adhesives (PSA) and two-part
epoxies. These boots, tapes and adhesives have various
drawbacks.
[0006] The utility of boots and tapes is subject to the quality of
application or installation and great care must be taken in
preparing and installing them. Boots and tape can be dangerously
unreliable if not installed properly. The usefulness of these
products is very dependent on the nature of the substrate (the
surface of the airfoil), to which they are applied. Different
substrates (different surfaces of helicopter blades or airplane
wings) have different inherent surface properties and have to be
handled accordingly. A boot or tape requires a very clean surface
in order to stick to a surface, and it may be difficult to get the
surface sufficiently clean. Even small amounts of coatings or
contaminants on a surface (especially near a tape or boot edge) can
prevent proper adherence. A helicopter blade or airplane wing
surface may have paint or another slippery coating or paint or a
residual contaminant (such as hydraulic fluid, lubricant, silicone
oil, other oils, etc.) on it that would prevent the tape or boot
from sticking to it. The blade or wing surface may need to be
specially prepped and contaminants may need to be completely
removed with special chemicals, cleaners, or treatments. Proper
installation if a boot or tape may require special equipment and a
controlled, clean environment. Even a relatively small area of a
tape or boot that is not adhered may cause problems, particularly
if the poor adherence occurs along a boot or tape edge or other
high stress area. In addition to unclean or slippery areas, air
bubbles may form during installation and prevent the boot or tape
from sticking to the surface. Boot or tape installation that
proceeds without proper surface preparation may cause boot or tape
failure with disastrous results. Airfoils are subject to tremendous
wind forces, and it is very dangerous if a protective material such
as a boot or tape becomes loose and falls off mid-flight. Even
beyond airfoil damage due to erosion, a boot or tape that falls
even partially off a helicopter blade may get caught in or
otherwise damage a helicopter rotor or tail rotor or even stop one
of the rotors altogether, interrupting flight or even bringing down
the entire helicopter.
[0007] Once in place, a boot or tape needs to not interfere with
flight aerodynamics. In particular, tapes and boots need to fit
closely on the airfoil during normal use and maintain the
aerodynamic properties of the helicopter or airplane. Once a tape
or boot is in place on a foil, the tape or boot material and the
adhesive start to age. Adhesives are temperature dependent and
decay over time, but it is difficult to predict exactly when that
will be. Physical properties of an adhesive, such as peel strength
and shear strength, are greatly affected by both hot and cold
temperatures. Commercial and military aircraft are used in harsh
environments all over the world and often operate at both ends of
the temperature spectrum in a single day, subjecting the adhesives
and protective materials to great stresses. Boots and tapes have
edges (which are typically found on the trailing edge of a foil)
that can disrupt airflow and change flight behavior. These edges
are also vulnerable to getting pulled on and pried up by tremendous
wind forces when an adhesive starts to fail, dislodging the boot or
tape from the foil mid-flight. A whole section of tape or boot may
be pulled away. Even detaching a small area of tape from a
helicopter blade can lead to severe vibration and dangerous
consequences for the helicopter and pilot. Tape that completely or
partially detaches from a helicopter blade can becomes entangled in
the helicopter tail rotor, and may cause a crash. In a combat
situation, if the occupants are lucky enough to survive the crash,
being stranded behind enemy lines is equally life threatening.
[0008] Boots and tapes wear out over time and can be difficult to
remove and replace. As mentioned above, the quality of boot and
tape installation is highly dependent on the airfoil surface and
the quality and nature of the surface changes over time. An
unprotected blade surface or a protective boot or tape on an
airfoil is damaged by abrasion and wear from sand and pebbles,
aging and regular use, corrosion from salt water, damage from
weapons, oxidation damage, ultraviolet (UV) light damage from the
sun, or weathering and cracking due to heat and cold exposure. A
tape or boot may not fit well onto a damaged blade surface. The
foil surface may have, in addition to coatings, paint, and
contaminants that can interfere, bits of an old boot or tape stuck
to it. Erosion may have left behind only adhesive or may have
broken the tape or boot down into numerous small pieces of adhered
film; these small bits can be very difficult to remove. For optimal
performance, all of a used tape or boot has to be completely peeled
off a blade before a new one is installed. Removal may require
special equipment, specific cleaners, or a special (clean)
environment. Cleaning all tape and residue from the surface may
require use of a wallpaper streamer or a sander or other abrasive
methods and the cleaning and sanding processes may further damage
the blade. Relying on an adhesive to secure a protective layer to
an airfoil is not an optimal solution.
[0009] Abrasion strips made of metal, such as nickel, stainless
steel or titanium, are also sometimes used on helicopter blades to
protect the blades from erosion. These are typically applied to the
leading edge of an airfoil, generally covering the first 15% of the
chord length on the top and bottom. In the highest wear areas, a
metallic cap, such as electroformed nickel that is tapered to a
thin trailing edge so as to reduce impact to airfoil performance is
bonded on top of an abrasion strip. In addition to many of the
problems described above with adhering boots and tapes to a foil,
metallic abrasion strips are softer than sand, and when a
helicopter blade is hit by sand, the sand can rapidly erode the
metal strip. The erosion of these strips is especially noticeable
on the outboard sections of the blade where tip velocity approaches
Mach 1. Additionally, as documented during combat operations in
Afghanistan, the erosion of a metal strip caused by powerful and
rapidly moving sand can cause the formation of a visible halo or
corona around the rotating helicopter blade. This corona effect, as
it is called, is thought to occur due to static discharge or to the
creation of a cloud of small metal particulates that ignite,
causing a spontaneous and visible spark due to pyrophoric
oxidation. The highly visible halo is spectacularly and undesirably
visible in the dark at night as a large, bright circle. The corona
effect makes the helicopter visible from a great distance which is
particularly detrimental for a helicopter that needs to be
stealthy.
[0010] Spray coatings are also sometimes used to protect helicopter
blades. As with the tapes and boots, careful surface preparation is
critical. A helicopter blade may need to be removed from the
helicopter for spray coating installation and hung in a special
spray booth. The blade has to be carefully cleaned in order for the
spray coating to stick to the surface. A spray coating is generally
applied to a blade in a liquid form in the spray booth. Areas of
the blade that should not be coated have to be protected or masked
to prevent coating. Multiple rounds of coating and drying are
generally required. Special controls are required to ensure that
the coating is applied with a unifomi thickness. Once applied,
these coatings may be thin and wear away quickly and need frequent
replacement. They may provide inadequate protection against harsher
environments or objects. Using such coatings reduces operational
readiness and allows fewer missions to be run.
[0011] Thus there is need for improved methods to protect an
airfoil, hydrofoil, or other foil and to extend the life of these
foil surfaces. Provided herein are articles, materials, and methods
for protecting moving parts from degradation, such as by protecting
an airfoil or hydrofoil from erosion forces from sand, sun, water,
or wind.
SUMMARY OF THE DISCLOSURE
[0012] The present invention relates to systems, articles,
materials, and methods for protecting objects from degradation and
particularly for protecting airfoils, hydrofoils, other foils, and
foil shaped objects such as from airplane wings, boat hydrofoils,
and helicopter blades from erosion forces such as sand, sun, water,
or wind. In general, such systems may use a shapeable covering that
has a continuous outer perimeter (e.g., without seams and without
ends) that circumscribes (or is configured to circumscribe) and
conforms to a surface of a foil. A shapeable covering may be a
sleeve with an opening at one end and may fit (or be configured to
fit) over a foil and change size to conform to the foil surface.
The continuous perimeter may be hold the sleeve together and hold
the sleeve on the foil. The sleeve may be mechanically interlocked
and held onto the foil by forces between the sleeve and the foil
(e.g., a compressive force, an interfacial force, static friction
or friction, etc.). Part or all of a shapeable covering may change
size to fit over a foil and may change size again to conform to the
foil surface when over the foil. In some cases, a portion of a
shapeable covering, such as a portion configured to fit over a
concave portion of a foil, may not change size or shape while the
rest of the sleeve does change size or shape. A shapeable covering
may include a polymer, such as a shape-memory or elastomeric
polymer, and may configured to expand in response to an applied
force and to contract in response to removal of the applied
force.
[0013] One aspect of the invention provides an erosion-resistant
sleeve for protecting a foil, the foil including an airfoil or
hydrofoil having a first foil shape, the sleeve including: a body
adapted to cover at least a portion of the foil, the body
comprising an outer surface and an inner surface and a sleeve
thickness therebetween and having a longitudinal dimension with a
first end and a second end and a dimension transverse to the
longitudinal dimension, the outer surface comprising a shape memory
polymer or an elastomeric polymer with a materially continuous
perimeter circumscribing the body around the transverse dimension
and having a second foil shape, the inner surface comprising a
third foil shape that has the same shape as at least a portion of
the first foil shape; and an opening at the first end of the body
adapted to receive the foil.
[0014] In some embodiments the first and/or third foil shapes
comprise a wing-like curvilinear foil shape or a double wedge foil
shape. In some embodiments, the body is seamless. In some
embodiments, the body is endless in the transverse dimension. In
some embodiments, the body further includes an opening at a second
end. In some embodiments, the body includes a concave portion. In
some such embodiments, concave portion includes a non-shape memory
material. In some embodiments, the first foil shape, the second
foil shape, and/or the third foil shape are substantially the same
and in some embodiments, they are different. In some embodiments,
the sleeve having a third foil shape is adapted and configured to
provide a lift force when the sleeve covers the foil and the foil
moves relative to an air or water current. In some embodiments the
foil includes a leading edge and a trailing edge and the sleeve is
adapted to surround and cover the foil at a portion of the leading
edge, a portion of the trailing edge, and an area between the
edges. In some embodiments, the thickness varies from a first
portion of the body to a second portion of the body. In some
embodiments, the foil includes a rounded leading edge at the front
of the foil and a trailing edge at the rear of the foil and the
thickness is greater at the first portion corresponding to the
rounded leading edge.
[0015] In some embodiments the foil and the inner surface of the
body are substantially the same size and in some embodiments the
inner surface of the body is smaller than the foil. In some
embodiments, a transverse segment of the body is adapted to undergo
a first expansion change from about 1% to about 75% in the
transverse dimension. In some embodiments, a transverse segment of
the body is adapted to undergo a first expansion change to provide
between 0.010'' and 0.25'' of clearance between the inner surface
of the body and the foil. In some embodiments, a transverse segment
of the body is adapted to undergo a first contraction change from
about 1% to about 75% in the transverse dimension. In some
embodiments, a transverse segment of the sleeve is adapted to
undergo a first contraction change to remove between 0.010'' and
0.25'' of clearance between the inner surface of the body and the
foil when the sleeve is in place over the foil. In some
embodiments, a transverse segment of the body is adapted to undergo
a first expansion change in response to an expansion force to
provide clearance between the inner surface of the sleeve and an
outer surface of the foil, and to contract when the force is
removed and thereby deliver a compressive force over the surface of
the foil when the sleeve is in place over the foil.
[0016] In some embodiments, the outer surface of the body is
substantially free of folds and wrinkles.
[0017] In some embodiments, the body includes a heat-responsive
shape-memory polymer and the body is configured to undergo a
shape-memory change in response to heat. In some embodiments, the
sleeve includes a thermoplastic polyurethane material. In some
embodiments, the sleeve has a shore hardness value from 60 A to 70
D. In some embodiments, the sleeve includes an aliphatic
polyurethane with a durometer hardness around 60 Shore D. In some
embodiments, the sleeve includes Tecoflex.RTM. (an aliphatic
polyurethane with a durometer hardness around 93 Shore A). In some
embodiments, the sleeve includes an aliphatic thermoplastic
polyurethane including at least one of polycaprolactone and
polycarbonate.
[0018] In some embodiments, the sleeve includes a plurality of
layers. In some embodiments, the sleeve thickness is between 0.1
mil to 120 mil or between 0.3 mil to 30 mil.
[0019] In some embodiments, the sleeve includes a channel, hole,
and/or wire through the body. In some embodiments, the sleeve
includes an adhesive on the inner surface of the body and/or a
coating on the outer surface of the body. In some embodiments, the
sleeve includes a P-static dissipative material, a radar
interference material, a radar reflective material, and/or a
metal.
[0020] Another aspect of the invention provides an
erosion-resistant stimulus responsive shape-memory polymer sleeve
for protecting a foil having a first foil shape, the sleeve having
a first configuration with a second foil shape and adapted to have
an expanded second configuration and a contracted third
configuration and including: a body having a longitudinal dimension
with a first end and a second end and a dimension transverse to the
longitudinal dimension; an opening at the first end of the body; an
outer surface and an inner surface with a thickness therebetween;
and the body is adapted to expand from about 1% to about 75% along
a transverse segment in the transverse dimension to change from the
first configuration to the expanded second configuration and to
shrink from about 1% to about 75% along the transverse segment in
the transverse dimension from the expanded second configuration to
the contracted third configuration when the sleeve is in place over
the foil.
[0021] In some embodiments, the first foil shape includes a
wing-like curvilinear foil shape or a double wedge foil shape. In
some embodiments, the body is seamless. In some embodiments, the
body further includes an opening at a second end. In some
embodiments, the body includes a concave portion (e.g., a non-shape
memory material). In some embodiments, the first foil shape and the
second foil shape are substantially the same and in some
embodiments they are different. In some embodiments, the third
configuration is further adapted and configured to provide a lift
force when the sleeve covers the foil and the foil moves relative
to an air or water current.
[0022] In some embodiments, the foil includes a leading edge and a
trailing edge and the sleeve is adapted to surround and cover the
foil at a portion of the leading edge, a portion of the trailing
edge, and an area between the edges. In some embodiments, the
thickness varies from a first portion of the body to a second
portion of the body. In some embodiments, the foil includes a
rounded leading edge at the front of the foil and a trailing edge
at the rear of the foil and the thickness is greater at the first
portion corresponding to the rounded leading edge.
[0023] In some embodiments, the body includes a heat-responsive
shape-memory polymer and the body is configured to undergo a
shape-memory change from the first configuration to the expanded
second configuration in response to heat. In some embodiments, the
body includes a heat-responsive shape-memory polymer and the body
is configured to undergo a shape-memory change from the expanded
second configuration to the contracted third configuration in
response to heat.
[0024] In some embodiments the foil and an inner surface of the
body are substantially the same size. In some embodiments, the body
includes an inner surface and the inner surface is smaller than the
foil.
[0025] In some embodiments, a transverse segment of the body is
adapted to undergo a first expansion change to provide between
0.010'' and 0.25'' of clearance between the inner surface of the
body and the foil when the body changes from the first
configuration to the expanded second configuration. In some
embodiments, a transverse segment of the sleeve is adapted to
undergo a first contraction change to remove between 0.010'' and
0.25'' of clearance between an inner surface of the body when it is
in the expanded second configuration and the foil when the sleeve
is in place over the foil.
[0026] In some embodiments, the body is adapted to deliver a
compressive force over the surface of the foil when the sleeve is
in place over the foil and the body is in the third configuration.
In some embodiments, the outer surface of the body is substantially
free of folds and wrinkles.
[0027] In some embodiments the sleeve includes a plurality of
layers. In some embodiments, the sleeve thickness is between 0.1
mil to 120 mil or between 0.3 mil to 30 mil.
[0028] In some embodiments, the sleeve includes a channel or hole.
Some embodiments include a coating on the outer surface of the
body. Some embodiments include an adhesive on the inner surface of
the body. Some embodiments include a wear indicator (e.g., in or as
part of an inner layer). Some embodiments include a wire, a
P-static dissipative material, and/or at least one of a radar
interference material and a radar reflective material. Some
embodiments include a metal. In some embodiments, the body includes
a thermoplastic polyurethane material (e.g., with a shore hardness
value from 60 Shore A to 70 Shore D). In some embodiments, the body
includes an aliphatic polyurethane with a durometer hardness around
60 Shore D. In some embodiments, the body includes Tecoflex.RTM.
aliphatic polyurethane with a durometer hardness around 93 Shore A.
In some embodiments, the body includes an aliphatic thermoplastic
polyurethane of polycaprolactone and/or polycarbonate.
[0029] Another aspect of the invention provides erosion-resistant
sleeve for protecting a foil, the foil including an airfoil or
hydrofoil having a first foil shape, the sleeve including body
covering at least a portion of the foil, the body including an
outer surface and an inner surface and a sleeve thickness
therebetween and having a longitudinal dimension and a dimension
transverse to the longitudinal dimension, the outer surface
including a materially continuous perimeter circumscribing the foil
around the transverse dimension and having a second foil shape, the
inner surface including the first foil shape, and the body has been
contracted from a larger size to a smaller size to conform around
the foil.
[0030] In some embodiments, the first foil shape includes a
wing-like curvilinear foil shape or a double wedge foil shape. In
some embodiments the body is seamless. In some embodiments, the
body further includes an opening at a second end. In some
embodiments, the body includes a concave portion (such as, for
example, a non-shape memory material).
[0031] In some embodiments, first foil shape and the second foil
shape are substantially the same and in some other embodiments,
they are different. In some embodiments, the second foil shape is
adapted and configured to provide a lift force when the sleeve
covers the foil and the foil moves relative to an air or water
current. In some embodiments, the foil includes a leading edge and
a trailing edge and the sleeve is adapted to surround and cover the
foil at a portion of the leading edge, a portion of the trailing
edge, and an area between the edges.
[0032] In some embodiments, the thickness varies from a first
portion of the body to a second portion of the body. In some
embodiments, the foil includes a rounded leading edge at the front
of the foil and a trailing edge at the rear of the foil and the
thickness is greater at the first portion corresponding to the
rounded leading edge.
[0033] In some embodiments, the body includes a heat-responsive
shape-memory polymer and the body underwent a shape-memory change
in response to heat.
[0034] In some embodiments, the foil and the inner surface of the
body are substantially the same size.
[0035] In some embodiments, a transverse segment of the body
underwent a first contraction change from about 1% to about 75% in
the transverse dimension. In some embodiments, a transverse segment
of the sleeve underwent a first contraction change to remove
between 0.010'' and 0.25'' of clearance between the inner surface
of the body and the foil.
[0036] In some embodiments, a transverse segment of the body is
configured to deliver a compressive force over the surface of the
foil.
[0037] In some embodiments, the outer surface of the body is
substantially free of folds and wrinkles.
[0038] In some embodiments, the sleeve includes a thermoplastic
polyurethane material. In some embodiments, the sleeve has a shore
hardness value from 60 A to 70 D. In some embodiments, the sleeve
includes an aliphatic polyurethane with a durometer hardness around
60 Shore D. Some embodiments include Tecoflex.RTM. (an aliphatic
polyurethane with a durometer hardness around 93 Shore A). Some
embodiments include an aliphatic thermoplastic polyurethane
including at least one of polycaprolactone and polycarbonate.
[0039] Some embodiments include a plurality of layers. In some
embodiments, the sleeve thickness is between 0.1 mil to 120 mil or
between 0.3 mil to 30 mil.
[0040] Some embodiments include a channel or hole through the body.
Some embodiments include a coating on the outer surface of the
body. Some embodiments include an adhesive on the inner surface of
the body. Some embodiments include a wire, a P-static dissipative
material, a metal and/or at least one of a radar interference
material and a radar reflective material.
[0041] Another aspect of the invention provides a method for
installing an erosion-resistant sleeve on a foil including the
steps of: inserting the foil into the sleeve through an opening in
the sleeve; contracting the sleeve around the foil; and conforming
the sleeve around the foil. In some embodiments, conforming
includes substantially covering the entire foil with the
sleeve.
[0042] In some embodiments the sleeve includes a body having a
longitudinal dimension with a first end and a second end and a
dimension transverse to the longitudinal dimension and the step of
contracting includes heating the sleeve to contract an inner
transverse segment of the body from about 1% to about 75% in the
transverse dimension.
[0043] In some embodiments, the step of conforming includes
providing an external sleeve surface that is substantially free of
wrinkles and folds.
[0044] In some embodiments, the step of contracting includes
contracting the entire sleeve around the foil. In some embodiments
the foil includes a concave portion and a non-concave portion and
the step of contracting includes contracting the sleeve over the
non-concave portions the method further including maintaining the
shape of the sleeve corresponding to the concave portions of the
foil. In some embodiments, the step of contracting includes
progressively contracting the sleeve from the first end of the
sleeve to the second end of the sleeve. In some embodiments, the
step of contracting includes applying a stimulus to the sleeve and
thereby contracting the sleeve.
[0045] In some embodiments, the sleeve includes a shape-memory
polymer and the step of applying a stimulus includes applying
energy to the shape-memory polymer and thereby contracting it. In
some embodiments, the step of applying energy to the shape-memory
polymer and thereby contracting it includes applying one of
convective heat, conductive heat and infrared energy.
[0046] In some embodiments, the sleeve is elastically dilated by an
applied force and the step of contracting includes removing the
applied force and thereby shrinking the sleeve.
[0047] In some embodiments, the step of conforming includes
creating a compressive force between the foil and the sleeve. In
some embodiments, the step of conforming includes creating an
interference fit between the inner surface of the sleeve and the
outer surface of the foil.
[0048] In some embodiments, the step of conforming includes
conforming the sleeve around the foil without using an adhesive
between the sleeve and the foil and in some other embodiments, the
step of conforming includes adhering the inner surface of the
sleeve to outer surface of the foil with an adhesive.
[0049] Some embodiments include the step of expanding the sleeve
prior to the inserting step and thereby creating clearance between
the sleeve and the foil.
[0050] In some embodiments, the foil includes a helicopter rotor
blade or a helicopter tail blade, and the step of inserting the
foil includes inserting the foil while the blade is attached to the
helicopter.
[0051] Another aspect of the invention provides a method of
protecting a foil with an erosion-resistant sleeve from erosion
including the steps of: moving the foil enclosed within the sleeve
relative to a media, the sleeve including an outer surface and an
inner surface and a sleeve thickness therebetween and having a
longitudinal dimension with a first end and a second end and a
dimension transverse to the longitudinal dimension, the outer
surface including a shape memory polymer or an elastomeric polymer
with a materially continuous perimeter circumscribing the body
around the transverse dimension and having a second foil shape;
subjecting the foil with the sleeve to an erosion force from the
media; and preventing a portion of the foil covered by the sleeve
from eroding.
[0052] In some embodiments the step of preventing includes eroding
a portion of the sleeve in response to the erosion force.
[0053] In some embodiments, the foil includes an airfoil, and the
method further includes moving the airfoil through air during
airfoil use that provides lift to an attached machine while
protecting the airfoil from damage from the air.
[0054] Some embodiments include the step of protecting the airfoil
from at least one of rain, sand, and snow. In some embodiments, the
foil includes a hydrofoil, and the method further includes
protecting the hydrofoil from damage from the water.
[0055] In some embodiments, the foil includes a hydrofoil and the
method further includes the step of moving the hydrofoil through
water during hydrofoil use that provides lift to a connected
machine while protecting the hydrofoil from damage from the
water.
[0056] Some embodiments include the step of inserting the foil into
the sleeve through an opening in the sleeve; contracting the sleeve
around the foil; and conforming the sleeve around the foil prior to
the using a foil step.
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] FIG. 1A shows a helicopter with protective sleeves over the
main rotor blades and tail rotor blades.
[0058] FIGS. 1B-1C show variations of protective sleeves over
helicopter rotor blades.
[0059] FIG. 2 shows a perspective view of the protective sleeve
shown in FIG. 1B.
[0060] FIG. 3A shows a cross-sectional view of a protective sleeve
over a rotor blade.
[0061] FIG. 3B shows a detail view of part of the protective sleeve
and blade shown in FIG. 3A.
[0062] FIGS. 4A-4B show, respectively, a rotor blade and a
protective sleeve that conforms to a rotor blade.
[0063] FIGS. 5A-C show how a protective sleeve can be expanded,
placed over a rotor blade, and contracted around the blade.
[0064] FIGS. 6A-B show a protective sleeve with a variable
thickness that fits on a rotor blade.
[0065] FIGS. 7A-7B show how a protective sleeve is placed over a
rotor blade.
[0066] FIG. 8A shows a cross-sectional view of a protective sleeve
over a rotor blade that has a concave region on its surface.
[0067] FIG. 8B shows a detail view of part of the blade shown in
the box in FIG. 8A.
[0068] FIG. 8C shows a protective sleeve configured to fit over a
concave rotor blade such as the blade shown in FIG. 8A.
[0069] FIGS. 9A-9Y show examples of various foil shapes that a foil
or a protective sleeve as described herein to protect a foil may
have or may take.
[0070] FIGS. 10A-10B show a view of a rotor that a protective
sleeve as described herein may protect.
DETAILED DESCRIPTION
[0071] Described herein are systems, articles, materials, and
methods for protecting an item from degradation and particularly
for protecting a moving part such as an airfoil or hydrofoil from
erosion. A system may include a sleeve that fits over the foil and
minimizes or prevents contact between a force of erosion and the
foil. A sleeve of a system may have a materially continuous
perimeter that circumscribes or is configured to circumscribe the
item in need of protection. The materially continuous perimeter may
enable forces that hold the sleeve in place on the item even
against strong counterforces that would otherwise remove the sleeve
from the item. A sleeve of a system may include a shapeable
covering with an expanded configuration and a contracted
configuration that is placed over the item in the expanded
configuration and contracted to the contracted configuration to
conform to the surface of the item. A sleeve may conform to the
outside surface of the foil when it is on the foil. A sleeve may
provide forces that hold the sleeve in place on the foil, even when
the foil is subject to harsh conditions such as a sandstorm or fast
moving wind or when part of the sleeve is damaged or missing. Such
a sleeve may provide various advantages especially compared with
existing protection systems, such as providing better foil
protection, having an ability to remain on the foil even under
adverse conditions, being easier or faster to remove or install,
preventing a corona effect, and so on.
[0072] FIG. 1A shows helicopter 2 with rotor blade 4 of a main
rotor and tail rotor blade 6 of a tail rotor. The rotor blade has a
(first) foil shape and, when in use, provides an aerodynamic lift
force to move the helicopter. FIGS. 1B-1C shows rotor blades such
as those shown in FIG. 1A partially covered and circumscribed by
protective sleeves as described herein. FIG. 2 shows a perspective
view of the sleeve shown in FIG. 1B without the rotor blade.
[0073] FIG. 1A also shows rotor blade 4 circumscribed and mostly
covered by sleeve 8 and tail rotor blade 6 circumscribed and mostly
covered by tail rotor sleeve 10. Sleeve 8 or tail rotor sleeve 10
may protect the rotor blade or tail rotor blade, respectively, from
damaging forces while the helicopter is in flight as well as when
it is on the ground. Damaging forces may include general
environmental and weather forces often considered erosion forces,
such as hail, lightning, rain, rocks, sand, snow, sunlight, and
wind that can act on the blade and cause blade damage and erosion.
Damaging forces may include other natural or non-natural forces,
such as a moving object such as an animal, a bird, a bullet, a
fragment, other debris, pebbles, shards, shot, shrapnel, or shock
or other waves, etc. Helicopter movement may cause or may increase
the frequency and intensity of damaging forces. For example, when a
helicopter rotor blade spins very fast (e.g., on the order of up to
500 revolutions per minute), and is engaged to generate a lift
force (e.g., the helicopter travels through the air at speeds up to
250 miles per hour (mph)), a helicopter blade encounters objects
with higher frequency and intensity than it does when it is on the
ground. These forces may be especially noticeable during take-off
and landing when pebbles and ground debris are forced against the
blades and can cause severe localized damage. Forces that damage a
rotor blade change the blade shape and integrity, preventing it
from working properly, and disrupting flight. Sleeve 8 provides a
covering or barrier that at least partially covers the rotor blade
and protects it from damaging forces. As shown in FIG. 1B and FIG.
2, sleeve 8 has two dimensions: a first (longitudinal) dimension 12
and a second (transverse) dimension 11 transverse to the
longitudinal dimension. A sleeve length in the first dimension
extends from first opening 14 at first end 15 of the sleeve to
second opening 17 at second end 18 of the sleeve. The open first
end may be useful for allowing the blade to be attached to the rest
of the rotor (e.g., attaching or connecting the blade to the rotor
shaft), for allowing access to the helicopter main rotor to which
the blade is connected etc., but in general is useful for placing
the sleeve over the rotor blade. The open second end may be useful
for positioning the sleeve over the blade, for preventing sleeve
wrinkling, or for exposing a portion of a blade. For example a lip
of a blade may be covered by a different material or different
covering. A sleeve may have a foil shape on its outer surface
(e.g., a second foil shape; the first foil shape referring to the
shape of a foil that the sleeve may cover) or inner surface (e.g.,
a third foil shape) or on both surfaces. The first, second, and
third foil shapes may be any, such as, for example, one of the foil
shapes described below and may be the same or may be different from
each other. In some examples, a sleeve may have a wing-like
curvilinear shape, and may have one or more of an angle, a bend, a
curve, a twist, a windswept end or tip, etc. As indicated above,
sleeve 8 (and the rotor blade) has a second (transverse) dimension
11 transverse to the first (longitudinal) dimension (e.g., in a
dimension shown by a line segment falling on the plane indicated by
A-A or a plane substantially parallel to A-A). Sleeve 8 has a
materially continuous perimeter circumscribing blade 4 in the
transverse dimension. Sleeve 8 goes around (e.g., all the way
around) the outside of blade 4 as a continuous material (e.g.,
without an end and without a seam). A transverse cross-section of a
sleeve exhibits a defined inner area. In general, a sleeve as
described herein will have a first (longitudinal) dimension, and a
second dimension transverse the first dimension with a materially
continuous perimeter that circumscribes or is adapted to
circumscribe an item. The description of foil and sleeve dimensions
as "longitudinal" and "transverse" are to some extent for
convenience and simplicity: while a longitudinal length of a sleeve
(or foil) will generally be longer than a transverse distance or
length of a sleeve (or foil), a longitudinal length may in other
cases be shorter than (or the same as) a transverse distance or
length. In general, a transverse dimension of a sleeve is the
dimension that is materially continuous and a transverse dimension
of an object is the dimension circumscribed (circumscribable) by
the transverse dimension of the sleeve. In other words, a sleeve
may be relatively long (like a shirt sleeve) or relatively short
and narrow (like a rubber band). Similarly, a length of the sleeve
in a longitudinal dimension may be longer than, the same length, or
shorter than a perimeter length (e.g., that goes all the way
around) in the transverse dimension.
[0074] FIG. 1C shows another variation of a sleeve on a rotor
blade. A rotor blade (not visible in this view) is covered and
circumscribed by sleeve 31, but in this variation the sleeve has a
closed second end 40 that forms windswept tip 38 at the end of the
rotor blade. Similar to sleeve 8 described above, sleeve 31 has two
dimensions: a first (longitudinal) dimension 32 and a second
(transverse) dimension 33 transverse to the longitudinal dimension.
Sleeve 31 has first opening 36 at first end 34 that may be useful
for sleeve placement on a rotor blade or for other purposes, such
as those described above. The closed second end may be useful for
protecting the end of the blade from damaging forces, for
materially helping to hold the sleeve in place, for ensuring that
the sleeve does not have an edge that might otherwise be vulnerable
to forces that would tend to lift or remove the sleeve away from
the foil, or for any other purpose.
[0075] FIG. 3A shows a cross-sectional view of rotor blade 4 and
sleeve 8 through the plane shown by A-A in FIG. 1B, and FIG. 3B
shows a detail view of the section 21 of the sleeve and foil shown
in box 19 in FIG. 3A. Sleeve 8 has a materially continuous
perimeter circumscribing the sleeve body around the second
(transverse) dimension 13. The materially continuous perimeter of
sleeve 8 also circumscribes blade 4 around a transverse dimension
of the blade (e.g., a materially continuous outer surface that
circumscribes a transverse dimension or line segment of the blade
falling on the plane indicated by A-A or a plane substantially
parallel to A-A in FIG. 1B). FIG. 3B shows sleeve 8 apposed to and
conforming to outer surface 23 of blade 4. FIGS. 3A and 4A also
shows rotor blade 4 with leading edge 26 and trailing edge 24. As
shown in
[0076] FIGS. 3A and 4B, sleeve 8 is adapted to surround and cover
blade 8 at a portion of the leading edge, a portion of the trailing
edge and an area between the edges.
[0077] FIGS. 4A-4B shows a cross sectional views of rotor blade 4
and sleeve 8, respectively through the line shown by A-A in FIG.
1B. The sleeve and rotor blade are separated from each other for
illustration purposes. The size and shape of inside surface 42 of
rotor blade sleeve 8 is the same size and shape as outer surface 44
of rotor blade 4. In general, the sleeve (e.g., the inner surface
of a sleeve) conforms to the surface of the blade it circumscribes.
The (first) foil shape of the rotor blade is the same as the
(third) inner foil shape of the sleeve. In this view, the (second)
outer foil shape of the sleeve is also the same as the first and
second foil shapes, but in other variations may be different
shapes. A blade may include one or more features, such as markings,
sensors, wear bars, etc. that may be considered to be part of the
blade.
[0078] FIGS. 5A-C show successive cross-sectional views of putting
a protective sleeve on a rotor as the sleeve is expanded, a rotor
blade is inserted, and the sleeve is contracted to conform to the
rotor blade. Sleeve 50 has been manufactured in a first, relatively
smaller size and is configured to be expanded to fit over the foil
and then to contract to conform around the foil. In particular,
sleeve 50 is configured to change size and/or shape to go from a
first size with a first sleeve shape to a second size with a second
sleeve shape and then to a third size with a third sleeve shape. A
sleeve may change size and shape to go from a relatively smaller
first size (first sleeve shape) to a relatively larger second size
(second sleeve shape) for inserting the foil into the sleeve, and
then to a third size with a third sleeve shape that fits onto
(conforms to) the surface of the foil. A sleeve having the
relatively smaller first size may have an inner surface and/or an
outer surface that are smaller than the second size and/or smaller
than the foil. As shown in FIG. 5A, sleeve 50 has outer surface 52,
inner surface 54 and sleeve thickness 56 between the inner and
outer surfaces. Sleeve 50 is provided or manufactured at a
relatively small first size. As shown in FIG. 5A, sleeve 50 in a
first configuration is expanded to form sleeve 50' having a
(second) expanded configuration sufficient to allow a foil to be
inserted into sleeve 50 (e.g., with sufficient clearance between
the blade and the inner surface of the sleeve). (Items or features
in the drawings that are changed in configuration are shown by the
addition of prime marks (', '', etc.)). As explained below, all or
only part of sleeve 50 may be expanded. In other words, part of
sleeve 50 may be expanded to form sleeve 50' and part may be left
unexpanded (e.g., in a first size or first shape or configuration
that is not expanded) as long as expansion of the sleeve as a whole
allows sufficient clearance between the sleeve and the foil so that
the foil can be inserted into the sleeve. In FIG. 5C, a foil (not
shown in this view) to be protected (or enclosed) was inserted into
expanded sleeve 50' and expanded sleeve 50' in the second
configuration is contracted around the foil to form contracted
sleeve 50'' in the third configuration. As explained below, all or
only part of sleeve 50' may contract around the foil. Part of a
sleeve may not contract (e.g., may remain in an uncontracted or
first shape or configuration). All or only part of the sleeve may
change shape and the entire sleeve may still fit or conform around
the foil.
[0079] A sleeve may be configured to provide a force to a foil to
hold the sleeve and foil together. A sleeve may contract less than
a maximum amount it is configured to contract (or which is capable
of contracting) in order to provide a force, such as a compression
force, against a foil when the sleeve contacts the foil. As
illustrated in FIGS. 5A-5C, sleeve 50'' is larger than sleeve 50.
Sleeve 50'' may apply a compressive force onto a blade when in
place on the blade. Sleeve 50'' may be held in a slightly expanded
configuration by a foil. The foil prevents the sleeve from fully
contracting back to its first size. When the sleeve is on the foil,
the inner surface of the sleeve body and the foil may be generally
the same size and same shape. For example, the inner surface of the
contracted sleeve may generally conform to the size and shape of
the foil, but there may be an irregularity or feature between them
such as an irregular surface (dent or hole) on the foil, a thin
adhesive layer, a small feature such as a sensor or wear bar
between the surface of the sleeve and the foil, etc. In other
examples, the sleeve may fit around and conform to the foil without
any irregularity or feature between them. An outer (and inner)
surface of a sleeve may be substantially free of surface
irregularities (e.g., folds or wrinkles) during sleeve formation or
when a sleeve is in place on a foil. In such cases, there may be an
occasional irregularity (e.g., fold or wrinkle) as long as it does
not substantially negatively impact foil aerodynamics. Generally,
an outer surface of a sleeve on a foil will be substantially smooth
and aerodynamic.
[0080] In some variations, and as mentioned above, a sleeve as
described herein may expand or stretch (or be configured to expand
or stretch) to fit over a foil. As shown in FIGS. 5A-5B, sleeve 52'
has been expanded from its contracted configuration shown by sleeve
50 to fit around a foil. The sleeve may be expanded in a
cross-sectional dimension by elongating part or all of a perimeter
(wall) of the sleeve in a dimension transverse to a longitudinal
dimension. As shown in FIG. 5A, a sleeve may be expanded by
elongating in a transverse dimension transverse segment 62 shown in
box 64 of the sleeve perimeter. A transverse segment of a sleeve
may expand in a dimension that generally follows chord 58 and/or
width 60 of a sleeve and part or all of a sleeve perimeter may be
expanded. A sleeve thickness may be increased or remain unchanged,
but in general a sleeve thickness may be slightly decreased as a
sleeve is expanded. A transverse segment of the body may be
expanded (or be adapted to undergo an expansion change) or
lengthened to more than 0% to 300%, from 1% to 250%, from 1% to
100%, to about 1% to about 75%, from 5% to 75%, from 10% to 50% in
the transverse dimension (as the sleeve changes from the first
configuration to the second configuration). A transverse segment of
the body may be expanded (or be adapted to undergo an expansion
change) to provide between 0.01'' and 2'' of clearance, between
0.010'' and 1'' of clearance, between 0.010'' and 0.5'' of
clearance, between 0.010'' and 0.25'' of clearance, etc. between
part or all of an inner surface of the sleeve body and the
foil.
[0081] An expanded sleeve, such as sleeve 50' shown in FIG. 5B, may
have any inner surface having an internal shape or any outer
surface having an external shape that allows a foil to be inserted
into it, but generally both the inner and outer surfaces of a
sleeve will have foil shapes. In some examples, the inner and outer
surfaces may have same foil shape. For example, it may be easier to
manufacture a sleeve that has the same inner and outer foil shapes
or the desired (final) shape of the sleeve may be easier to control
if the inner and outer foil shapes of the sleeve are the same
during sleeve placement on the foil. In some examples, the inner
and outer surfaces may instead have different shapes. For example,
a portion of the sleeve may be thicker in some places than in other
places creating different inner and outer surface shapes. For
example, a foil may be configured to change the shape that would
otherwise be presented by a uncovered blade alone, such as
providing more or less concavity in the (final) foil shape,
providing sharper or blunter leading or trailing edges, and so on.
A thickness of the sleeve body may vary from a first portion of the
sleeve body to a second portion of the sleeve body. FIG. 6A shows
foil 104 with leading edge 126 at the front of the foil and
trailing edge 124 at the rear of the foil. FIG. 6B shows sleeve 108
adapted to fit around foil 104 Inner surface 142 of sleeve 108 fits
around outer surface 144 of foil 104. Sleeve leading edge 130 is
adapted to fit over foil leading edge 126 and sleeve trailing edge
128 is adapted to fit over foil trailing edge 124. The thickness of
the sleeve may be thicker at first portion 131 of the body to a
second portion 133 of the body. FIGS. 6A-6B also show rounded
sleeve leading edge 130 at the front of the foil has a greater
thickness than does sleeve trailing edge 128 at the rear of the
foil (or than at other portions of sleeve 108).
[0082] In some variations, and as mentioned above, a sleeve as
described herein may contract (or be configured to contract) to
conform to a foil. As shown in FIGS. 5A-5B, sleeve 52' has been
expanded from the configuration of sleeve 50 to fit around a foil.
The sleeve may be contracted to conform to the foil. The sleeve may
be contracted in a cross-sectional dimension by contracting part or
all of a perimeter (wall) of the sleeve in a dimension transverse
to a longitudinal dimension. As shown in FIG. 5B, a sleeve may be
contracted by contracting or shortening in a transverse dimension a
transverse segment of the sleeve perimeter. As shown in FIGS.
5B-5C, a transverse segment of a sleeve may contract in a dimension
that generally follows chord 58' and/or width 60' of a sleeve and
may encompass part or all of a sleeve perimeter. A transverse
segment of the body of may be contracted or shortened (or be
adapted to undergo a contraction change or shortening) to conform
the transverse segment (and remainder of the sleeve) around a foil
(not shown in this view), as shown in FIG. 5C by contracted segment
62'' in box 64''. The segment shows relative to both chord 58' and
width 60'. A transverse segment of the body of may be contracted or
shortened (or be adapted to undergo a contraction change or
shortening) from about 1% to about 75%, 0.1% to 100%, 1% to 50%, 5%
to 50%, and so on in a transverse dimension. A transverse segment
of the body may be contracted (or be adapted to undergo a
contraction change) to remove between 0.01'' and 2'' of clearance,
between 0.010'' and 1'' of clearance, between 0.010'' and 0.5'' of
clearance, 0.010'' and 0.25'' of clearance between the inner
surface of the body and the foil when the sleeve is in place over
the foil. An entire sleeve may be contracted at one time or may be
contracted in stages or in a continuum over time. For example, an
entire sleeve may be contracted essentially at one time by removing
a force or providing a stimulus that affects or acts on the entire
sleeve. In other examples, a sleeve may be contracted (sequentially
or continuously) from a first end to a second end, such as from a
closed end to an open end. In other examples, a sleeve may first be
contracted in a central portion of a sleeve and contraction
continued towards both the first end and the second end. For
example, starting the contraction in the middle may make it easier
to prevent or remove wrinkles while starting the contraction on an
end may make it easier to fit a sleeve over a swept tip end. A
transverse segment such as shown in any of FIGS. 5A-5C may be
configured to expand, to contract, or both at different times. A
transverse segment of a sleeve such as described herein may undergo
(or be adapted to undergo) a first expansion change in response to
an expansion force to provide clearance between an inner surface of
the sleeve and an outer surface of foil, and to contract when the
force is removed or when a stimulus is applied and thereby deliver
a compressive force over the surface of the foil when the sleeve is
in place over the foil. A sleeve material may undergo or be
configured to undergo contraction or expansion, or both. (Some
portions of a sleeve material may not or may not be configured to
undergo contraction or expansion). In some examples, a material
such as an elastomeric material may be configured to expand and
contract more than once (a plurality of times). Such expandability
and contractibility may aid, for example, in wrinkleless sleeve
placement over foil. In some examples, a sleeve may expand (or be
configured to expand) in a longitudinal dimension (such as along
longitudinal dimension 12 or longitudinal dimension 32 shown in
FIGS. 1A-1B). Longitudinal expansion may be useful, for example to
better fit a sleeve over a foil or to help place a sleeve over an
irregular portion of a foil (such as over a foil tip that is
twisted). Longitudinal expansion may be between 0% and 20%, from 1%
to 15%, from 1% to 10%, etc. In some examples, a sleeve may be
configured to not expand and/or contract in a longitudinal
dimension. Preventing such change may make it easier to place a
sleeve on a foil in a desired location without forming wrinkles or
creating an area of sleeve overlap.
[0083] A sleeve on a foil, such as sleeve 50'' shown in FIG. 5C,
may be held on a foil in any way that prevents the sleeve from
coming off the foil, but in general may be (mechanically) secured
to the foil by an interference fit (e.g., a friction fit) between a
sleeve and the foil. An interference fit may be between an inner
surface of a sleeve and an outer surface of a foil. In some
examples, as a sleeve encircles (a cross-section of) a foil shaped
article, and can remain affixed to the foil shaped article without
any adhesive (e.g., without a pressure-sensitive adhesive, epoxy,
2-part or multi-part epoxy) between the sleeve and the foil. A
sleeve may be shaped onto a foil so that the inner surface of the
sleeve slightly intercalates into surface irregularities on the
outer surface of the foil. Such irregularities may be microscopic
or larger than microscopic in scope. A sleeve may not be able to be
"peeled off". A sleeve may be secured or held onto the foil by a
continuous (endless) material which material is held together by
chemical bonds (e.g., covalent bonds, ionic bonds, etc.). A sleeve
material may include a single material or may include two (or more)
materials graded into one another so as to create a continuous
material without an end. A material may, for example, have no
sudden or discontinuous changes in one or more chemical, material,
or physical properties, such as chemical stability, coefficient of
friction, compressive strength, flexural modulus, glass transition
temperature, hardness, plasticity, resilience, refractive index,
roughness, shear modulus, shear strength, specific modulus,
specific strength, specific weight, etc. around a transverse
dimension or throughout a sleeve. Affixing without a
pressure-sensitive adhesive may make installation easier with fewer
concerns over substrate preparation, and may allow installation in
challenging environments without the need for as much special
equipment, special cleaners, or a special environment. It may also
prevent problems due to the presence of residual adhesive residue
(from removing an old sleeve) that might otherwise interfere with
placement or performance of a new or replacement sleeve on a foil.
In some examples, an adhesive (e.g., a pressure-sensitive adhesive,
epoxy, 2-part or multi-part epoxy, etc.) may hold or help hold some
or all of a sleeve onto a foil. An adhesive may be placed between
some or between essentially all of a sleeve and a foil. A pressure
sensitive adhesive may adhere to a surface with slight pressure. It
may or may not require activation by heat, solvent, water, etc. A
pressure sensitive adhesive may create an immediate bond upon
application and be more or less permanent. In other cases, a
pressure sensitive adhesive may be removable or allow for
repositioning of a material on a substrate being adhered without
leaving adhesive on the substrate or delaminating part of the
substrate. It may form a bond that remains tacky for a long time. A
sleeve may be prevented from moving (e.g., longitudinally and/or
transversely) due to static friction between the inner surface of
the sleeve and the outer surface of a foil shaped article (e.g., a
normal force or force transverse to the surface). Engagement of
these surfaces may be caused by the interference fit. A sleeve may
not prematurely detach without failure of the sleeve itself. A
sleeve and foil shaped article may be held together at least in
part by any covalent bonding, interactive force or interfacial
force, such as dipole-dipole interaction, hydrogen bonding, ionic
bonding, van der Waal forces, etc. A smooth inner surface of a
sleeve may be held onto a smooth foil surface such as by static
friction; a rough inner surface may be held onto a soft (or rough)
foil surface by mechanical interaction. In some examples, even if a
portion of a sleeve is broken off, damaged, torn, or otherwise
loosened from a foil shaped article, the sleeve may be held onto
the foil. For example, the mechanical interlocking force of the
sleeve encircling the foil shaped article may hold the sleeve on
the foil.
[0084] An interference fit may be achieved, for example, using a
sleeve made of a shapeable material such as shape-memory material
and/or an elastomeric material. A shape-memory sleeve may be formed
to size to have a cross-sectional dimension equivalent to or
slightly smaller than a cross-sectional dimension of the
foil-shaped article to be covered by the sleeve. The sleeve may be
dilated and temporarily fixed (stabilized) in a
dilated/expanded/stretched state to facilitate sleeve application
to a foil. Such a sleeve may be applied to the foil shaped article
by sliding the sleeve over the object. Heat or another stimulus may
be applied to the sleeve to return the sleeve to (or close to) its
original size. An elastomeric sleeve may be formed to have a
cross-sectional dimension equivalent to or slightly smaller than a
cross-sectional dimension of a foil shaped article to be covered.
An elastomeric sleeve may have elastic behavior, and may be
configured to be deformed by an applied (expansion) force and to
exhibit recovery if the force is removed. An elastomeric sleeve may
be elastically "dilated" by application of a force along the sleeve
body (or walls). An elastomeric sleeve may be applied via a
mechanical means or via creation of a pressure differential between
the interior and exterior of a sleeve. An elastomeric force applied
to a sleeve may generally be below the elastomeric material's
elastic limit; e.g., below the highest stress that can be applied
without producing a measurable amount of plastic (non-recoverable)
deformation. After successfully positioning the sleeve on a foil,
the applied force may be removed and the elastomeric sleeve allowed
to conform to the foil surface. An elastomeric sleeve on a foil may
still be elastically dilated, though to a lesser degree than when
the applied force was being applied.
[0085] A contracted sleeve, such as sleeve 50'' shown in FIG. 5C,
may have any inner surface having an internal shape or any outer
surface having an external shape that may protect the foil, but
generally both the inner and outer surfaces of a sleeve will have
foil shapes. In some variations, the inner and outer surfaces may
have same foil shape. For example, it may be it may be easier to
manufacture a sleeve that has the same inner and outer foil shapes
or the desired (final) shape of the sleeve may be easier to control
if the inner and outer foil shapes are the same. In some examples,
the inner and outer surfaces may instead have different shapes. For
example, the inner surface may conform to the foil surface and the
outer surface may provide a new overall foil shape when it is on
the foil (e.g., it may change the foil shape otherwise presented by
the blade alone, such as providing more or less concavity in the
foil, sharper or blunter leading or trailing edges, features in an
area of the foil, additional material on a portion of the sleeve
that may be subject to greater forces, etc.). In some examples, an
outer surface of a sleeve may have a lower coefficient of friction
(COF) than an inner surface of a sleeve. Such a sleeve may
facilitate holding the sleeve to the foil while providing excellent
aerodynamic capability.
[0086] A method of installing an erosion-resistant sleeve on a foil
may include inserting the foil into the sleeve through an opening
in the sleeve; contracting the sleeve around the foil; and
conforming the sleeve around the foil. A shape-memory polymer
sleeve may be contracted, for example, by applying a stimulus
(convective heat, conductive heat, energy, heat, infrared energy
etc.) to the shape-memory polymer and thereby contracting. An
elastically dilated sleeve (an elastomeric sleeve) dilated by an
applied force may be contracted, for example, by removing the
applied force and thereby shrinking or contracting the sleeve.
[0087] In some variations, a sleeve, such as the one shown in FIGS.
5A-5C, may have the same shape during different steps of being
placed on a foil (blade). The inner (and/or outer surfaces) may
have the same shape in the first, second (expanded), and/or third
(contracted) configurations. For example, a sleeve may be
manufactured, uniformly expanded for placing over a foil, and
uniformly contracted onto the foil, maintaining the shape of the
sleeve throughout the different steps. In some variations, a
sleeve, such as the one shown in FIGS. 5A-5C, may have different
shapes at different steps. For example, as described elsewhere
herein in more detail, a sleeve may be non-uniformly expanded so
that only a portion of the sleeve is expanded, thus changing the
internal and external shapes of the expanded sleeve relative to the
first (e.g., manufactured or initial shape). An expanded sleeve may
be non-uniformly contracted so that only a portion of the sleeve is
contracted or so that one portion is contracted to a greater extent
than another area, thus changing the internal and external shapes
of the contracted sleeve relative to the expanded sleeve. Such
non-uniform contraction may be useful, for example, for providing
better contact with a concave area of a foil or for covering a
feature on a foil or blade. The third configuration of sleeve 50''
may have or may be adapted and configured to provide a lift force
or drag force when the sleeve covers the foil and the foil moves
relative to a media current (e.g., relative to an air current, a
water current, etc.).
[0088] A sleeve may also be elongated in longitudinal dimension
(e.g. elongating between some or all of a first end of the sleeve
to a second end of a sleeve such as from sleeve first end 17 to
sleeve second end 14 in FIG. 1B). In some examples, a sleeve may
not be elongated (or configured to elongate) in a longitudinal
dimension. A sleeve may be elongated in at least one dimension by
applying a force to the sleeve. It may be more difficult to fit a
sleeve elongated in a longitudinal dimension to a foil. In some
cases, it may be more difficult to control contraction in the
longitudinal dimension to fit the sleeve around the foil. In some
cases, longitudinal elongation and contraction may provide a better
fit and additional force to hold the sleeve and foil together.
[0089] In some variations a sleeve as described herein may contract
(or be configured to contract) to conform to a foil. FIG. 7A shows
sleeve 70 which is larger than and configured to fit over and
protect a foil. Sleeve 70 may, for example be manufactured in this
relatively larger size. The sleeve may be contracted to sleeve 70'
to conform to the foil, as described above for other variations.
The sleeve may be contracted in a cross-sectional dimension by
contracting part or all of a perimeter (wall) of the sleeve in a
dimension transverse to a longitudinal dimension. As described
above for other variations, a sleeve may be contracted by
contracting or shortening in a transverse dimension a transverse
segment of the sleeve perimeter. As shown in FIGS. 7A-7B a
transverse segment of a sleeve may contract in a dimension that
generally follows the directions indicated by chord 158' and/or
width 160' of a sleeve and may encompass part or all of a sleeve
perimeter that circumscribes a sleeve in a transverse dimension. A
transverse segment of the body of may be contracted or shortened
(or be adapted to undergo a contraction change or shortening) to
conform the transverse segment (and remainder of the sleeve) as
shown in FIG. 7B around a foil (not shown in this view) similar to
the contraction shown in FIGS. 5B-C.
[0090] In some variations, an adhesive may be used for holding a
sleeve onto a foil. An adhesive may be placed between a foil and a
sleeve. An adhesive may be placed on an inner surface of a sleeve
or an outer surface of a foil. An adhesive may be placed in between
substantially any area between which the sleeve and the foil are
apposed. An adhesive may be placed in between a subsection of the
areas between which the sleeve and foil are apposed. For example,
adhesive may be placed near an end of a sleeve, such as near first
end 14 or second end 17 of sleeve 8 in FIG. 1B but not along the
entire longitudinal dimension 12. A sleeve and a foil held together
by an adhesive may be held using any method (covalent or
non-covalent bonds, etc.).
[0091] A sleeve as described herein may be removable and
replaceable without removing a foil (e.g., a helicopter rotor
blade, etc.) that it covers from an object such as a helicopter.
Such sleeves may reduce costs, prevent rotor damage, increase
operational readiness etc.
[0092] A helicopter blade or other foil provides a lift or drag
force to move a helicopter or another machine through air, water or
another media. A blade with a sleeve generally provides a lift or
drag force to move an object through a media. A sleeve that covers
a blade (e.g., a sleeve that is a contracted and conformed around a
blade as described herein) may be adapted and configured to provide
a lift or drag force when the sleeve covers the blade or other
foil, and the blade or other foil moves relative to air, water, or
other media (e.g., relative to an air or water current). In some
variations, a sleeve may cover an item that does not have a foil
shape and the sleeve may provide a foil shape. Such a sleeve may be
adapted and configured to provide a lift or drag force when the
sleeve covers the item and the item with the sleeve in place moves
relative to air, the environment, water or another media.
[0093] Described herein is a method of protecting a foil with an
erosion-resistant sleeve from erosion that may include the steps of
moving a foil enclosed within the sleeve relative to a media (e.g.,
air, a gas, a fluid, a gel, etc.), the sleeve including an outer
surface and an inner surface and a sleeve thickness therebetween
and having a longitudinal dimension with a first end and a second
end and a dimension transverse to the longitudinal dimension, the
outer surface including a shape memory polymer or an elastomeric
polymer with a materially continuous perimeter circumscribing the
body around the transverse dimension and having a second foil
shape; subjecting the foil with the sleeve to an erosion force from
the media; and preventing a portion of the foil covered by the
sleeve from eroding (e.g., from rain, sand, snow, sun, wind, etc.).
In some examples, the sleeve may erode in response to the erosion
force. In some examples, the sleeve may generally not erode (and
may be erosion-resistant or erosion-proof). In some examples, the
method includes creating friction between the foil and the sleeve
during foil use and thereby holding the sleeve against the foil. In
some examples the foil is an airfoil, and the method further
includes moving the airfoil through air during airfoil use that
provides lift to an attached machine (e.g., an airplane, a
helicopter, etc.) while protecting the airfoil from damage from the
air or other damaging forces. In some examples, the foil is a
hydrofoil, and the method includes protecting the hydrofoil from
damage from water and in other examples, the method includes moving
the hydrofoil through water during hydrofoil use that provides lift
to a connected machine (e.g., a boat, another watercraft, etc.)
while protecting the hydrofoil from damage from the water or other
damaging forces. The method may further include the steps of
inserting the foil into the sleeve through an opening in the
sleeve; contracting the sleeve around the foil; and conforming the
sleeve around the foil prior to the using a foil step.
[0094] A sleeve for a foil as described herein generally has a
materially continuous perimeter in a transverse dimension. Such a
perimeter generally has no seam and no end (e.g., is endless or
seamless without interruption) in the transverse dimension. A
sleeve may have no seam in any dimension. A sleeve may have one
edge (e.g., at a first end) or more than one edge (e.g., an edge at
a first end and an edge at a second end) and the edges may not meet
when a sleeve is on a foil. An edge may be smooth and may not have
any sharp turns. An edge may be thinner or thicker than or tapered
relative to adjacent portion of the foil A foil covered by a
covering may have a leading edge and a trailing edge, and the
sleeve (a materially continuous perimeter) may be adapted to
surround and cover the foil at a portion of the leading edge, a
portion of the trailing edge, and an area between the edges.
[0095] In some variations, an intervening layer, an inner surface,
or an entire covering may be seamless. Any of these layers may
include only one material or may include more than one material
joined together without a seam.
[0096] As described herein, a sleeve may be erosion protective and
may include an erosion-protective material. A sleeve may be adapted
and configured to protect a foil from erosion when the sleeve is in
place on a foil. A sleeve may include a material that is
preferentially eroded or preferentially erodes. A sleeve may
include an erosion-resistant material configured to resist erosion
and to not erode away or erode away more slowly than a foil subject
to the same forces of erosion. A sleeve (e.g., an eroded sleeve)
may be removed and may be replaced with a new sleeve. A sleeve may
include an erosion-protective material configured to preferentially
erode and thereby protect a foil which it covers.
[0097] A sleeve as described herein may be a shapeable covering. As
mentioned above, a sleeve may be made from a material that has
changed its size and/or shape or is configured to change its size
and/or shape to fit onto or conform to the size and shape of a
foil. A sleeve may be made from a material that fits onto (conforms
to) a foil and provides protection may be used. While in some
examples, all sleeve material may conform to or be configured to
conform to the shape of the foil, in other examples only a portion
of the sleeve material may conform or be configured to conform to
the foil. For example, as described elsewhere herein, portions of
the material may not change shape such that they fit onto a concave
portion of a blade. Such a portion may be a shape-memory material
that is not contracted, or may be a non-shape memory material
(e.g., elastomeric or a plastic polymer) in a substantially
shape-memory sleeve. For example, part of a sleeve may be made of
another material that provides other features or functionalities
(such as radar absorbing materials, thermally conductive materials,
etc.).
[0098] A sleeve may be made using any process or combination of
processes to create the sleeve, create layers, create or add
features, etc., such as co-extrusion, dip-coating, extrusion,
heat-sealing, multi-layer extrusion, overlaying, over-the-wire
extrusion, spraying, transition extrusion welding, etc. Extrusion
or any other process may be used to add a feature such as adding a
channel, a stripe, a through-hole (axial void or "lumen"), a wire,
etc. or a layer to a sleeve, which may be added at the same time as
the sleeve is formed or may be added afterwards. Additional
features or layers may be added by dipping, laminating, spraying,
etc. Two or more layers may be joined together, such as by using a
primer or adhesive (tie-layering). The thickness of a sleeve may be
varied, for example by using transition extrusion so that one
portion of a sleeve is thicker than another portion. Equipment for
performing such processes is known in the art, such as extrusion
equipment and manufacturing processes from Davis Standard, etc.
[0099] In some variations, a sleeve may include a shape-memory
polymer or shape-memory alloy. A sleeve may also include other
materials. A shape-memory polymer of a sleeve will generally be a
stimulus-responsive shape-memory polymer configured to change shape
in response to an applied external stimulus. An applied external
stimulus may be, for example, energy, such as conductive heat,
convective heat, electricity, energy, heat, infrared energy, light,
magnetism, moisture (e.g., a solution), etc. A shape-memory polymer
may be a `heat-shrink` polymer. A shape-memory polymer may have the
ability to change from a first (also referred to as original,
rigid, glassy, or "permanent") state to a second (also called
temporary or rubbery) state and then back to (or close to) the
first (original or "permanent") state. A material's glass
transition temperature T.sub.g is the temperature at which this
reversible transition between the glassy state and the rubbery
state occurs. (The glass transition temperature is generally seen
as a large drop (in the storage modulus, when viewed on a log scale
against a linear temperature scale). However, a sleeve made from a
shape-memory polymer as described herein may be prevented from
fully returning to its original shape. Instead, a sleeve may only
attempt to return to its original shape and may therefore provide a
force against a foil to hold the foil on the sleeve.
[0100] As indicated above, in some examples a sleeve made from a
shape-memory polymer, placed on a foil in a second (temporary,
stable) shape and subject to an applied external stimulus, may be
prevented by the foil from fully returning to its original shape,
and may instead have a third shape (which generally may be larger
than the first shape but smaller than the second shape). In its
third shape, a sleeve may provide a compressive (and/or other)
force against the foil to thereby hold the sleeve onto the foil.
Such changes in the foil shape may be controlled by the application
(and removal) of an applied external stimulus, such as by heating
and then cooling. (Other intermediate shapes may also be made). The
following is an example of a sleeve made from a heat-responsive,
shape-memory polymer, but similar principles may be applied to a
sleeve that includes another type of stimulus-responsive shape
memory polymer. A heat-responsive shape-memory polymer sleeve is
made that has a first glassy phase (modulus) below a glass
transition temperature, T.sub.g and a rubbery phase (modulus) above
a T.sub.g. A sleeve is made of a shape-memory polymer in a first
(original or "permanent") configuration or shape with the formation
of physical crosslinks. The sleeve is subject to heating above the
T.sub.g, expanded and shaped to fit over a foil, and cooled while
holding it in this second expanded and shaped configuration (e.g.,
to hold the sleeve in a temporary but stable state). After placing
the sleeve on a foil, the sleeve may be changed back to its first
shape (or close to its first shape as described herein) by again
heating the sleeve, generally at or above the polymer's glass
transition temperature, and allowing the sleeve to recover (or
attempt to recover) its first shape or configuration to fit over
and conform to the surface of the foil.
[0101] A shape-memory polymer sleeve may be made by methods known
in the art, such as by extrusion, blow, compression, or injection
molding, solution-coating, vacuum-formation, etc. A method of
forming an erosion-protective sleeve may include the steps of
melt-extruding a shape-memory capable polymeric material to form a
sleeve; optionally applying an axial or longitudinal force to the
sleeve sufficient to elongate the sleeve (e.g., up to 10%, up to
20%, up to 30%, up to 50%, up to 70%, up to 100%, etc. and/or
described elsewhere herein) and cooling the sleeve while in the
elongated state (to impart a temporary, but stable elongation to
the sleeve); and/or optionally applying a dilatation force that
imparts a dilation of the sleeve body by expanding a wall of the
sleeve (e.g., by 1%-75% in a transverse dimension as described
elsewhere herein) and cooling the sleeve while in the dilated state
to impart a temporary but stable transverse expansion to the
sleeve. The longitudinally and transversely applied forces may be
applied at the same time or may be applied at different times.
[0102] A sleeve may include a shape-memory polymer such as, for
example, a branched polymer, a copolyester, a copolymer, a
cross-linked polymer, an ethylene-vinylacetate copolymer, a graft
polymer, a polyisoprene, a polymer, a polyurethane (segmented
polyurethane), a styrene-butadiene copolymer, a thermoplastic
polyurethane, etc. or combinations thereof. In some examples, the
body of the sleeve includes a heat-responsive shape-memory polymer
and the body is configured to undergo a shape-memory change in
response to heat. A shape-memory polymer sleeve may be shaped as
known in the art, such as described in Lendlein and Kelch,
"Shape-Memory Polymers", Angew. Chem. Int. Ed. 2002, 41, 2034-2057,
which is incorporated herein by reference. A polymer may be chosen
for a sleeve so that the sleeve has a desired combination of
qualities, such as abrasion resistance, adhesion strength, ease of
formation, ease of placement, erosion-resistance, useful T.sub.g
for applying a sleeve in the field. In some examples, a
shape-memory polymer in a sleeve may include a polyurethane, such
as a thermoplastic polyurethane. A polyurethane in a sleeve may be
a linear block copolymer and may include hard segments and soft
segments. Any hard or soft segments may be used as long as the
resulting sleeve can be placed over a foil shaped article and
formed around the article to protect the article. A hard segment in
a polyurethane sleeve as described herein may be made from (based
on a unit of) an isocyanate unit, such as an aliphatic isocyanate
or a linear isocyanate(4,4'-methylene bis(phenyl isocyanate (MDI),
hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI),
toluene diisocyanate (TDI), etc.) and a chain extender such as, for
example, ethylene glycol, 1,4-butanediol(1,4-BDO or BDO),
1,6-hexanediol, cyclohexane dimethanol, hydroquinone
bis(2-hydroxytethyl ether (HQEE), etc. that may be polymerized with
an isocyanate to form hard segments. A polyurethane soft segment
may be made from (based on) a adipic acid, another diol, another
polyol, a polyester-diol, polyester glycol, a polyester polyol, a
polyether. A polyurethane may also be cross linked. In some
examples, a sleeve may include a DiAPLEX polyurethane with a glass
transition temperature from 25.degree. C. to 90.degree. C.
(35.degree. C. to 80.degree. C., 45.degree. C. to 75.degree. C.,
etc.). Such a polymer may include a polyurethane having up to 600%,
up to 500%, up to 400%, up to 300%, up to 200%, up to 100%, or up
to 50% elongation in the rubbery phase and 30% to 50%, 20%-60%,
etc. elongation in the glassy phase. Such a polymer may include,
for example, a polyurethane with any of the characteristics shown
in Table 1.
TABLE-US-00001 TABLE 1 Pellet Type (MM) MM (Ether Type) 2520 3520
4520 5520 6520 7520 9020 Item Unit G R G R G R G R G R G R G R
Hardness H.sub.DD 78 26 77 30 76 30 77 27 76 35 76 35 73 25 100
Modulus MPa 3 2.3 1.4 2.1 1.2 1.2 1.2 T S MPa 45 12 51 10 55 10 48
13 48 13 48 13 48 13 Elongation % 30-50 >600 30-50 >600 30-50
>600 30-50 >600 30-50 >600 30-50 >600 30-50 >600 B M
MPa 2450 2450 2150 2150 1900 1900 1900 B S MPa 90 85 80 80 50 55 55
S G 1.25 1.25 1.25 1.25 1.25 1.25 1.25 T.sub.g .degree. C. 25 35 45
55 65 75 90 Where; G/R: Glass Region, R/R: Rubber Region, T S:
Tensile Strength, B M: Bending Modulus, B S: Bending Strength S G:
Specific Gravity, Tg: Glass Transition Temperature degree Celsius
indicates data missing or illegible when filed
[0103] As indicated above, shape-memory polymer sleeve as described
herein may be or may include a polyurethane. A shape-memory polymer
useful for a sleeve may be DiAPLEX MP 5510 with a soft phase
transition of 55.degree. C. or DiAPLEX MM 7520 with a soft phase
transition of 75.degree. C. (SMP Technologies Inc./Mitsubishi
Corporation/Mitsubishi Heavy Industries, Ltd.). A sleeve for
protecting a foil may be made from DiAPLEX MM 7520 polyurethane
resin, which may be made from diphenylmethane-4,4'-diisocyanate
(CAS 101-68-8), adipic acid (CAS 124-04-9), ethylene glycol (CAS
107-21-1), ethylene oxide (CAS 75-21-8), polypropylene oxide (CAS
75-56-9), 1,4-butanediol (CAS 110-63-4), and bisphenol A
(CAS-80-05-7) using manufacturing processes as known in the art. In
a particular example, a shape-memory polymer sleeve may be made,
for example, by melt-extruding shape-memory capable polymeric
material to form a shape-memory capable sleeve.
[0104] In some variations, a sleeve may be made from a
thermoplastic material, such as a thermoplastic (elastomeric)
polymer and have or be configured to have a first, second, and/or
third (or more than three) size and/or shape. A thermoplastic
polymeric sleeve will generally include an elastomeric polymer
configured to change shape in response to a change in force applied
to (or removed from) the sleeve. A thermoplastic sleeve may be
configured to expand up to twice its length in response to an
applied force. A size or shape may be changed by applying a force
or removing a force (applying a mechanical stress to the
elastomeric sleeve or removing a mechanical stress from the
thermoplastic sleeve). An elastomeric sleeve may have the ability
to change from a first (original) shape to a second (temporary)
shape and then back to (or close to) the first (original) shape.
Such changes may be controlled by the application (and removal) of
force, such as an expansion or deformation force (a pull or push).
As indicated above, in some examples, a sleeve made from a
thermoplastic polymer and held in a second (temporary) shape by an
applied force may be placed on a foil, and the applied force
removed to allow the sleeve to contract/shrink. However, the sleeve
may be prevented by the foil from returning fully to its original
shape, and may instead have a third shape. In its third shape on
the foil, a sleeve may provide a compressive (and/or other) force
to the foil and hold the sleeve onto the foil. A sleeve may include
a thermoplastic polymer such as, for example, an aliphatic
thermoplastic polyurethane, a butadiene, a branched polymer, a
copolyester, a copolymer, a cross-linked polymer, a fluoropolymer,
a graft polymer, a nylon, a polyacrylate, a poly-butadiene, a
polycaprolactone, a polycarbonate, a polychloroprene, a polyester,
a polyether, a polyisoprene, another polymer, a polyurethane
(segmented polyurethane), a polyvinyl chloride, a
styrene-butadiene, etc. or combinations thereof. A material for a
sleeve may be chosen based on various factors, such as ease of
applying the sleeve, durability, level of erosion resistance, etc.
A sleeve (sleeve material) may be made in any way that allows the
sleeve to be placed on a foil and provide protection. As described
elsewhere herein, a sleeve may have one layer or more than one
layer, and may have features, holes, etc. Various ingredients or
additives such as an accelerator, anti-oxidants, a curative, a
filler, a plasticizer, a scorch retarder, etc. may be used for
manufacturing an elastomeric polymer to add desired qualities, such
as chemical resistance, low temperature performance, strength
properties, etc. An elastomeric sleeve may be made using methods as
known in the art, such as, for example blow molding, compounding,
extrusion, injection molding, thermoforming, etc. For example, a
material for a sleeve, such a thermoplastic polyurethane (TPU) may
be chosen because it is abrasion or erosion resistant, flexible at
low temperatures, hard, heat resistant, high tear strength, etc.
Hardness Shore A and Shore D of a material may, for example, be
measured according to DIN 53505 (ISO 868). In some examples a
material having a shore hardness value from 40 Shore A to 100 Shore
D, 60 Shore A to 100 Shore A, from 40 Shore A to 80 Shore A, from 0
Shore D to 100 Shore D, from 60 Shore A to 70 Shore D etc. may be
useful. The choice of a particular material hardness may be
balanced with other sleeve features for a particular use. A harder
sleeve may be more difficult to shape but may provide better
protection against certain damaging forces. TPU is a highly
abrasion resistant elastomeric material. In some examples, a sleeve
may include an aliphatic thermoplastic polyurethane including
polycaprolactone (polyester) and/or polycarbonate. In some
examples, a sleeve may include an aliphatic polyurethane with a
durometer hardness around 60 Shore D. A thermoplastic sleeve may
include one or more of a Pearlthane polycaprolactone based
polyurethane, such as Pearlthane 11T80 shore hardness of 82 A 630%
elongation to Pearlthane 11T65D shore hardness of 64 D/440%
elongation (Merquinsa, a Lubrizol Company, Barcelona, Spain) and/or
Desmopan Range 55 A-74 D (abrasion test ISO 4649), Desmopan
polycarbonate grade 790 92 A-40 D 450% elongation, Desmopan
polycarbonate 795U 93 -43 D 430% elongation, Desmopan polyether
grade 955U 97 A-55 D 400% elongation, Desmopan polyether grade 9385
86 A-35 D 600% elongation (Bayer MaterialScience), Elastollan
thermoplastic polyurethane with shore hardness values from 60 A-70
D (BASF), thermoplastic polyurethane Tecoflex (Lubrizol). In some
examples, a sleeve may include an aliphatic polyurethane with a
durometer hardness around 60 Shore D. In some examples, a
thermoplastic sleeve may include Tecoflex (aliphatic polyurethane
with a durometer hardness around 93 ShoreA).
[0105] A sleeve may have any dimensions that provides sleeve
protection and does not interfere with desired foil use. A sleeve
thickness may be, for example, between 0.1 mil (0.0001'') to 120
mil, 0.3 mil to 30 mil, 0.1 to 10 mil, etc.
[0106] A sleeve may include or may have placed in or on it one or
more additions, features, or materials, such as an additive, an
adhesive a coating, a channel, a filler, a hole, etc. A sleeve as
described herein may be made from one, two or more than two types
of materials and may be a composite material. A sleeve may have
one, or more than one (a plurality) of layers. The layers may all
be the same size or an inner layer may be smaller than an outer
layer, such that the outer layer completely covers the inner layer
when in place on a foil. An outer layer may be attached to an inner
layer or an outer layer may hold a separate inner layer or feature
onto a foil with a compression force. A first material may have a
second material adhered, attached or embedded in it or placed in or
on it. A sleeve may include a wear resistant material such as a
ceramic\(e.g., for example, an oxide, a carbide, a nitrides, etc.),
a metal, a polymer, etc. A sleeve may include a radar absorbing
material, a radar reflective material, another radar interference
material, an infrared IR) absorbing material, an alignment
indicator (e.g., for example, a colored pigment, fluorescent
additive, ultraviolet (UV) additive, etc.), a wear indicator (e.g.,
for example, a colored pigment, a fluorescent additive, an
ultraviolet (UV) additive, etc.), an electrically conductive
material (e.g., for example, aluminum, carbon, silver, silicon
carbide, etc.), a thermally conductive material (e.g., for example,
aluminum, boron nitride, silicon carbide, etc.), a P-static
(precipitation static) dissipative material, a strengthening or
other fiber (e.g., for example, Kevlar.RTM. (aramid synthetic
fiber; DuPont), Spectra.RTM. (ultra-high-molecular-weight
polyethylene (UHMWPE); Honeywell), Zylon.RTM.
(poly(p-phenylene-2,6-benzobisoxazole (PBO), Toyobo), a metal, a
wire, etc. A fiber may add durability or may be configured to
preferentially wear away to protect the foil. An opening (hole or
channel) of a sleeve may be useful for aligning (the sleeve to the
foil) or for routing wires for heating, sensing, or for a
structural or lightning strike protective device. A wire, such as a
copper, nichrome, or nickel wire, may be useful for heating or
sensing, or as a structural or lightning strike protective device.
A feature or layer may be in or on an inner layer of a sleeve, an
outer layer of a sleeve, or in the middle of a sleeve.
[0107] A sleeve and/or foil may be treated or modified, such as
with an adhesive (which may on an inner surface of a sleeve or
between a sleeve and the foil), a coating (which may for example be
on an outer surface of a sleeve, etc.) A coating may be a thin
material applied in a liquid form, such as a paint, another
protector, etc. Sleeve characteristics may be chosen to maintain
weight balance and aerodynamic balance of foil or group of foils
(such as on a rotor blade).
[0108] Many (though not all) airfoils exhibit concave curvature.
Some shapeable sleeves (e.g., some shape-memory polymer sleeves or
elastomeric sleeves) may not be suitable for covering a foil
exhibiting concave curvature because they may stretch tightly over
the concave area. FIG. 8A shows a cross-section of sleeve 148 with
a body with a materially continuous perimeter circumscribing foil
144 in a transverse dimension 151 such as described herein. FIG. 8B
shows a close-up view of the section shown by the rectangular box
in FIG. 8A. Foil 144 includes concave region 154 (in the region
indicated by bracket 162). When a sleeve in an expanded
configuration is placed over a foil and the sleeve contracted to
form a contracted sleeve, a portion 158 of the sleeve (in the
region indicated by bracket 162) may pull tightly and bridge across
concave region 154 of foil 144, creating gap 160. In the region of
a gap, a sleeve does not follow the contour of the foil. A gap
between a sleeve and a foil may be undesirable and may cause
problems, such as poor adherence between the sleeve and the foil. A
gap may change (in an undesired way) the overall foil shape of an
item that has a sleeve in place relative to the foil shape of the
item alone. A gap may distort the foil shape. An aerodynamic or
hydrodynamic force such as lift or drag may be altered (reduced or
increased) due to the change in the foil shape. A gap may prevent a
sleeve from adhering to or holding onto a blade; a frictional force
or attractive force between molecules that might otherwise hold a
sleeve onto the blade in the concave region may be reduced or
absent and may cause the sleeve to fall off the item or otherwise
be susceptible to unwanted forces. FIG. 8C shows sleeve 168
configured to for placing on an item (a foil) that has a concave
region and for preventing (or reducing a size of) a gap from
forming between the sleeve and the concave region of the foil.
Sleeve 168 is generally configured to change size and/or shape but
may have one or more portions that are configured (or handled) to
not change their size or shape. These portions may not
stretch/expand and may not contract. Other portions of the sleeve
(e.g., portions that will coincide with predetermined areas of the
foil that are not concave) are configured to expand or otherwise be
in a temporarily (but stable) expanded configuration. Sleeve 168
(in an expanded configuration) is generally configured overall to
contract around a foil and fit onto the foil. First portion 170 of
the sleeve is generally configured to contract to fit around the
foil, while second portion 172 is configured to fit onto a concave
region of a foil without contracting (to prevent a gap from forming
between the sleeve and the foil during sleeve placement on the
foil). Second portion 172 may have a concave shape that corresponds
to a concave shape of a foil. In general, second portion 172 may be
configured to maintain its size and/or shape while first portion
170 contracts during sleeve placement and contraction to fit onto a
foil. Surprisingly, not all areas of a sleeve body needs to be
shaped (shapeable) in order to provide an interference fit of a
sleeve over a foil. In some variations, while first portion 170
contracts (is configured to contract) during overall sleeve
contraction, second portion 172 may not be contracted (e.g., may
remain uncontracted). As described above, a sleeve that is
expanded, may, prior to being expanded into its temporarily
enlarged state, be equivalent or smaller than the (cross-section)
of the foil it can cover.
[0109] In some variations, second portion 172 may change (be
configured to change) size and/or shape, but to a greater or lesser
degree than are other portions of the sleeve or may change at a
different time to accommodate the concave region of the item.
Second portion 172 may instead (also) have one or more focal points
around which material preferentially contracts to fit second
portion 172 onto a concave portion of a foil.
[0110] In some variations, a second portion of a sleeve configured
to fit onto a concave region of a foil, such as portion 172, may
include material having the same composition as do other portions
of the sleeve, but the material may be differently configured or
may be treated differently. For example, a sleeve made from a
shape-memory polymer may generally be configured to change from a
first configuration to a second (expanded) configuration, such as
shown in FIGS. 5A-5B. During this change, sleeve first portion 170
(FIG. 8C) may expand while sleeve second portion 172 may be
maintained unchanged (unexpanded) or may be contoured into a
concave shape. During the contracting step (when the sleeve is
contracted to fit around the sleeve), the second portion may remain
unchanged (e.g., because it is already in a concave configuration).
For example, although both first portion 170 and second portion 172
include a shape-memory polymer, second portion 172 may not be
subject to a shape-memory change stimulus and so may not change its
size or shape. Alternatively, second portion 172 may change
(contract) but to a less degree than does first portion 170. For
example, second portion 172 may be subject to a shape-memory change
stimulus (such as described elsewhere herein or as known in the
art), but it may be a weaker stimulus than applied to first portion
172. In some examples, a sleeve may include a first portion having
a shape-memory polymer (such as described elsewhere herein or as
known in the art) and a second portion having a non-shape-memory
polymer (such as described elsewhere herein or as known in the
art). A second portion may or may not change size and/or shape or
may change size and/or shape to a different degree or in a
different way relative to the first portion when a sleeve is being
expanded and/or when a sleeve is being contracted to fit around a
foil. A sleeve may include a first shape-memory portion configured
to contract around a foil and a second non-shape-memory portion
configured to maintain its shape when the first portion is being
contracted. The shape of the second portion may be, for example,
concave. Two or more materials such materials may be joined
together with a seamless (or seamed) joining. In another example, a
second portion in an elastomeric sleeve may include a elastomer
with different properties or a different shape. For example, the
second portion may be angled, curved, concave, thicker, thinner,
etc. so that the second portion fits to the concave region of the
foil when in position. The second portion may have a focal point(s)
or focal regions (such as at an inflection point, a minimum convex
function point, a maximum concave function point, etc.).
[0111] FIGS. 9A-9Y show examples of foil shapes. Foils in these or
other shapes may have need of protection and may be protected using
the systems, articles, materials, and methods described herein. An
article to be protected herein may be a foil, a foil shaped
article, or may be useful as a foil when a sleeve is placed over
it. A shapeable covering or sleeve as described herein may have a
foil shape or may take or be configured to take a foil shape, and
may cover one of the articles described above. A sleeve may provide
a foil shape to a foil or a non-foil shaped article. In general,
however, a foil shaped sleeve may be useful for covering or
protecting a foil shaped article. Different foils have different
configurations based on the planned use of the foil and there is
not one size that fits all purposes. Generally a foil has a leading
edge, which is a point at the front of the airfoil that has maximum
curvature and a trailing edge, which is a point of maximum
curvature at the rear of the foil. A straight line, called a chord
line, can be drawn that connects the leading edge and trailing
edge. Most foils also show camber, which is the asymmetry between
the top and bottom surfaces of the foil, although some foils may be
symmetric and not be cambered. A sleeve may be continuous around
the leading edge, the upper surface, the trailing edge, and the
lower surface and may be shaped to cover (fit to) the camber. FIG.
9A shows foil 200 with leading edge 202 and trailing edge 204.
Chord line 206 connects leading edge 202 and trailing edge 204 and
may be useful for describing characteristics of a foil. Foil 200 is
cambered and has an upper surface camber 208 and a lower surface
camber 210 which is different from upper surface camber 208. The
foil camber may determine how a foil moves through a media, such as
air. FIG. 9B shows foil 230 with media 232 movement strongly and
predominantly along upper surface 234. FIG. 9C shows foil 240 with
media 242 movement along upper surface 244 and lower surface 246.
Foil shapes have changed over time as understanding of aerodynamics
and fluid dynamics evolved. For example, early airfoils had a
concave lower surface, such as shown in FIG. 9J, and produced great
lift. Such airfoils, however, lost speed while producing lift and
other designs were better for high speed flight, such as those
shown in FIGS. 9K-9O. More recently, airfoils having a concave
surface have found favor again to take advantage of the high lift
provided by the concave surface. For example, some airfoils are
used in conjunction with leading edge (Kreuger) flaps or trailing
edge (Fowler) flaps to change the airfoil into a concave shape to
provide high lift. In general, a foil is a body configured to or
able to provide a desired reaction force when in motion relative to
a surrounding media (e.g., aqueous solution, air, gel, water etc.).
An airfoil or hydrofoil is generally a shaped surface that produces
a lifting force ("lift") that acts at right angles to an airstream
or water stream and a dragging force ("drag") that acts in the same
direction as the airstream or water stream when moved relative to
the airstream. A high-speed aircraft often employ thin, low-drag,
low-lift airfoils; slow aircraft may often use thicker airfoils
with high drag and high lift. An airfoil may be found for example,
on an airplane, a bird, a boat (e.g., a sailboat) a glider, a
helicopter, a toy, a wind turbine, etc. and may include a blade, a
propeller, a tail, a wing, etc. A hydrofoil may be found, for
example, on a bird (e.g., a diving bird), a boat, a fish, another
water craft, etc. and may include a diving plane, a fin, a flipper,
a keel, a propeller, a rudder, a toy, a tail, a wing, etc.
Generally, a foil is moved past a media, but a media may also be
moved past a foil (such as in a wind tunnel). In some examples, a
foil may have a wing-like curvilinear foil shape or a double wedge
foil shape.
[0112] As indicated above, a sleeve as described herein may have a
longitudinal dimension and a transverse dimension and may cover or
be configured to cover a length of a foil and may circumscribe or
be configured to circumscribe a foil about its transverse
dimension. A sleeve to cover a foil and/or provide a foil shape to
an object may have any longitudinal and transverse dimension shapes
and sizes.
[0113] A sleeve may cover or be configured to cover part or all of
any helicopter (main or tail) rotor blade. The following are
non-limiting examples of helicopter blades that may be covered or
protected by a sleeve or for which a sleeve may be adapted and
configured to cover or protect. Such a blade may be, for example, a
high aspect ratio airfoil. It may be up to about 40 feet long, may
have up to a 30 inch chord, may be 1-3 inches thick, may have a
`swept` tip, and/or may have a twist (e.g., the airfoil
cross-section may change pitch along the blade). Table 2 shows
examples of dimensions that some sleeves may have or may take, such
a sleeve that is on or configured and adapted to be placed on a
helicopter blade.
TABLE-US-00002 TABLE 2 Sleeve geometry Min Max Units Example Length
0.1 100 Feet 1 50 2 25 Wall Thickness 0.1 120 Mil (0.001 in) 0.2 60
0.3 40 Perimeter 3.14 100 inches 6.26 85 inches 15 70 inches Ratio
of Length to 1:1 10:1 12'' length:12'' perimeter perimeter-120''
length:12'' perimeter 2:1 9:1 24'' length:12'' perimeter-108''
length:12'' perimeter 3:1 8:1 36'' length:12'' perimeter-96''
length:12'' perimeter
[0114] FIGS. 10A-10B shows perspective cross-section views of foil
256 that may be circumscribed by a sleeve. In one example, a chord
length 250 of the foil is about 20.76''. A portion of a sleeve may
be thicker around leading edge 254 to protect the leading edge. In
some examples, a sleeve as described herein may cover or be adapted
to cover and circumscribe a UH-60 Black Hawk rotor blade such as,
for example, having radius of about 322 inches, a nominal chord of
about 20.76 inches, a rectangular blade planform with a swept tip
and non-linear twist. In some examples, a sleeve as described
herein may cover or be adapted and configured to withstand an
operating speed of about 258 rpm, resulting in a hovertip Mach
number of about 0.65. Such a helicopter may have a 53.8' rotor
diameter with 4 blades (21'' chord) and carry or be configured to
carry, for example, 3 crew members and 11 passengers. In some
examples, a sleeve as described herein may cover or be adapted and
configured to cover a Sikorsky UH-60 Black Hawk rotor blade, such
as, for example, with a chord of 20.76 inches and a perimeter of
42-50 inches. In some examples, a sleeve as described herein may be
configured to cover a Sikorsky S-64 or S-64F Skycrane rotor blade,
such as, for example, with a chord length of about 2.167 feet or 26
inches. Such a helicopter may have a 72.3' rotor diameter with 7
blades (26'' chord). In some examples, a sleeve as described herein
may cover or be adapted and configured to cover a CH-53E rotor
blade, such as, for example, with a chord of 0.76 meters or 29.92
inches and a perimeter of 60-70 inches. Such a helicopter may have
a 79' rotor diameter with 30'' chord. In some examples, a sleeve as
described herein may cover or be adapted and configured to cover a
Robinson R22 rotor blade. A diameter of two blades connected by a
hub may be approximately 26 feet, and each with a chord of 7.2''
and having an -8 degree twist.
[0115] A sleeve, especially a helicopter sleeve, as described
herein may be configured to last at least 100 hours, at least 500
hours, at least 1000 hours, at least 1500 hours, or at least 2000
hours without failing during use (falling off or causing sufficient
vibration that prevents desired or normal use) and/or during
use/exposure to sand. A blade protected by a sleeve may last at
least 100 hours, at least 450 hours, at least 500 hours, at least
1000 hours, least 1500 hours, or at least 2000 hours without
failing during use and/or during use/exposure to sand. For example,
the U.S. Army may require a blade to last at least 450 hours over
sand. A sleeve may be placed on a foil during blade manufacture or
after manufacture, and may be replaced one, two, or three, or more
than three times. A sleeve may be replaced in the field or may be
replaced at a special depot. A sleeve may be placed on a foil when
the foil is separated from an object for which it can serve as a
foil or can be placed while the foil is attached to the object. For
example, a sleeve may be placed on a rotor blade while the blade is
attached to a helicopter or may be placed on a rotor blade that is
not attached to a helicopter.
[0116] As for additional details pertinent to the present
invention, materials and manufacturing techniques may be employed
as within the level of those with skill in the relevant art. The
same may hold true with respect to method-based aspects of the
invention in terms of additional acts commonly or logically
employed. Also, it is contemplated that any optional feature of the
inventive variations described may be set forth and claimed
independently, or in combination with any one or more of the
features described herein. Likewise, reference to a singular item,
includes the possibility that there are plural of the same items
present. More specifically, as used herein and in the appended
claims, the singular forms "a," "and," "said," and "the" include
plural referents unless the context clearly dictates otherwise. It
is further noted that the claims may be drafted to exclude any
optional element. As such, this statement is intended to serve as
antecedent basis for use of such exclusive terminology as "solely,"
"only" and the like in connection with the recitation of claim
elements, or use of a "negative" limitation. Unless defined
otherwise herein, all technical and scientific terms used herein
have the same meaning as commonly understood by one of ordinary
skill in the art to which this invention belongs. The breadth of
the present invention is not to be limited by the subject
specification, but rather only by the plain meaning of the claim
terms employed.
* * * * *